Nowadays it is usual to receive raw rubbish or waste in processing centres after a simple compacting operation which facilitates its transportation. It is already known, according to DE-OS-27 53 920, that in addition to this first compacting it is possible to carry out, in a compression chamber, multiple compressions using a plurality of pistons introduced into and then withdrawn from the compression chamber one after the other. Each of the pistons has a cross section less than that of the chamber and only partially compresses the rubbish situated in this chamber. In order to obtain correct pressing of the rubbish, it is necessary to multiply the number of pistons and to control their action over time so that all the rubbish situated in the chamber is compressed in turn. Such a device is costly and complex to use.
Generally, in waste processing centres, the inert materials such as metals, iron, etc, are extracted and the remaining rubbish is exploited, essentially by means of two types of technique.
A first type of exploitation consists of incinerating the rubbish or waste in order to recover heat energy used for producing steam under pressure (which can be used for urban heating, for local industrial consumption, for the requirements of public authorities, etc, or again for the production of electric power by means of turbine generator sets). However, such incineration as practised at present has several failings.
Firstly, the total exploitation yield is mediocre and, as far as the authorities are concerned, generally results in a relatively high financial charge because of the high depreciation of the investments compared with the modest actual recovery of heat energy. Moreover, the raw rubbish has to be processed immediately and the recovery yield is further reduced since deliveries of rubbish and periods of high energy needs do not coincide. In addition, the low profitability of this exploitation makes it necessary to limit costs, and incineration is currently carried out in grate furnaces: without superheaters it is not possible, with this type of equipment, to comply with the recent pollution standards laid down in the majority of industrialised countries, both with respect to the solid residues, which have to contain very little unburnt material and be non-polluting, and with regard to the gaseous effluent, which has to be clean (for example, for EC standards, must be capable of maintaining itself at a temperature of more than 850.degree. C. for more than 2 seconds).
In addition, another method of exploiting rubbish consists of taking advantage of the biomass which it contains in order to produce, by fermentation, composts, organic manure or gases. However, the methods of exploitation of this type are ill-suited to the processing of the above-mentioned raw rubbish consisting of a mixture of fermentable materials and combustible materials, and this handicap increases each year in industrialised countries because of the great increase in the proportion of non-fermentable materials in rubbish.
Consequently, at the present time, there is no satisfactory solution making it possible to process raw rubbish or waste in a manner which both complies with the pollution standards relating to the effluent and to exploit these materials profitably.